Although HIV-1 replication can be effectively suppressed with currently existing antiretroviral drugs, infection with HIV-1 remains incurable. This is primarily related to the ability of HIV-1 to establish a latent reservoir of HIV-1-infected CD4 T cells that is unresponsive to currently available antiretroviral agents. Pharmacological reactivation of active HIV-1 gene expression in latently infected cells can result in cellular deat due to cytopathic effects or immune mediated clearance, and represents one of the most promising and most clinically advanced strategies to target latently infected cells. Results from prior pilot clinical trials, conducted in collaboration with the applicants, demonstrate that the potent histone deacetylase inhibitor (HDACi) panobinostat is effective in reversing HIV-1 latency and transiently increasing plasma HIV-1 RNA in vivo. In addition, this work indicated that viral reactivation with panobinostat resulted in a 3-4 fold reduction of CD4 T cell-associated HIV-1 DNA in a subset of patients, and that this decrease was associated with delayed viral rebound kinetics during an analytical treatment interruption. Interestingly, a detailed analysis of immune parameters revealed that decrease of HIV-1 DNA during panobinostat treatment was unrelated to the magnitude or breadth of HIV-1-specific CD8 T cells, but instead strongly correlated to the proportion of activated innate effector cells, such as NK cells and plasmacytoid dendritic cells. Together, these data suggest that HDACi can be used effectively as latency-reversing agents, and that innate effector cell immune responses are critical for reducing the reservoir of latently infected cells when viral reactivation is pharmacologically induced. This project sets out to integrate these observations into a conceptually novel HIV- 1 eradication strategy that is based on treatment with panobinostat as a latency-reversing agent in combination with pegylated IFNa-2a as an innate immune activator. We hypothesize that the concomitant use of both agents leads to innate immunity-dependent elimination of latently infected cells in which viral reactivation is pharmacologically induced. Specific aim (SA) 1 will focus on conducting a pilot clinical trial in which n=30 ART-treated HIV-1 patients will be randomized 2:1 to treatment with panobinostat and PEG-IFNa-2a during four one-week cycles, each of them separated by a three-week observation period, or to four cycles of treatment with panobinostat alone. In SA 2, we will investigate how the combined treatment regimen influences CD4 T cell-associated HIV-1 RNA, plasma RNA, HIV-1 DNA levels and the frequency of cells harboring replication-competent HIV-1. SA 3 is designed to comprehensively analyze immune effects associated with decreases in viral reservoir size, using a novel high-throughput mass spectrometry approach in combination with gene expression profiling and functional assays. This study represents an interdisciplinary collaboration of investigators with complementary expertise in HIV-1 virology, immunology, pharmacology and clinical patient care, and will be highly informative for the development of clinical strategies aiming at HIV-1 eradication.